Base shield



W. R. JONES BASE SHIELD June 7, 1949.

Filed Dec. 17, 1946 MW g m R w 7 Z e u 5 MM w.

Patented June 7, 1949 BASE SHIELD Walter'R. Jones, Emporium, Pa.,assignor to Sylvania Electric Products, Inc.,. a corporation of.

Massachusetts Application December 1'7, 1946, Se'rial No. 716,785

8. Claims. 1

This invention. relates to electronic circuits, and has for its objectthe provision of novel shielding structures.

In order to prevent. undesirable interaction between the field atvarious points inhigh-gain amplifiers itv has longbeen the custom'toenclose such components as radio tubes and high-frequenoy coils inshielding'cans- Another-practice frequently used to minimize interactionof fields has been the provision. of numerous. terminals on the chassis.so that leads of minimum length may be used for connecting variouscircuit components to ground. The present invention proposes a shieldingcage combining the merits of both the shield can and the groundingterminals. A better understanding of this invention will be gained fromthe following disclosure of a preferred embodiment thereof and from the.drawings wherein:

Fig; 1 is a view of one form of novel shielding cage associated'wi-th asocket for an electronic tube, being a bottom view of its supportingchassis;

Fig. 2 is an elevation of one form of novel shield alone;

Fig. 3 is a perspective of this form of shielding cage during wiringoperations;

Fig. 4 is a bottom view of a chassis showing circuit application of amodification of the shielding cage in Figs. 1 to 3;

Fig. 5 is an enlarged detail of the cag in Fig. 4; and

Fig. 6 is a wiring schematic of the circuit application in Fig. 4.

Referring now to Figs. 1 to 3, a metal shielding cage is shown, made ofcopper or some other metal to which soldered connections may readily bemade. The shielding cage includes extensions ill by means of which thecage may be secured to the chassis, a more or less continuous series ofstrips l2 normally projecting away from the chassis, and a ring I 4connecting strips [2 to each other and to extensions I0. In Fig. 1 theshielding cage is shown secured by nuts IE to a chassis l8 inassociation with socket 2|] for a radio tube. The term radio tube ishere used in its commercial sense, extending to circuit components usednot only where radiant energy from antennae is involved but tooscillators, video amplifiers, audio amplifiers, combinations thereof,and to all circuit applications where the interaction of electromagneticor static fields is to be limited by shielding.

In the illustrated example there are eight strips l2, each of which hasa hole 22 so that a resistor 24' ora condenser 26' will always have agrounding terminal adjacent its socket terminal. 2%, socket 20 being ofthe octal variety. In Fig. 3, a few of the eight strips l2 are bent soas: towmake the socket terminals accessible for assembling and solderingthe resistors, condensers, and any other circuit leads required. Thesebent strips, l2 ordinarily are to be restored to their originalcondition extending, away from thezchassi s. Preferably strips 52 are ofsubstantial width, com.- pared to the spaces therebetween and in materrangement they are substantially as effective as a complete-shield forthe stray fields which might otherwise induce voltages into the circuitcom,- ponents and wiring connected-to the: tube: (not shown) in thesocket. The tube is conventionally shielded.

Portions It for. securing the shielding cage to the chassis, may be.provided. with lugs 2.8. having holes 30 and providing additionalgrounding terminals. The socket illustrated is of the lock-in varietyproviding a grounding terminal 32 for the central electricallyconductive shielding base of the radio tube. One of the groundingterminals 28 may be bent away from the chassis, and a short lead may beconnected between grounding terminal 32 and a grounding terminal 28.

In Figs. 4 to 6 there is shown a slight modification of the cage inFigs. 1 to 3. In Fig. 4 two stages of a high-frequency amplifier arephysically illustrated, and these are diagrammatically shown in Fig. 6.A pair of shielding cages 34 and 383 are shown associated with sockets38 and. 40, respectively, for tubes 42 and 44, which tubes are coupledby transformer 46 having condensers 48 and St for resonating the primaryand secondary windings. This circuit is entirely conventional, and isused to illustrate an application of the grounding cage. Interstagetransformer 46 and condensers t8 and 5!] are contained within ashielding can 52 (Fig. 4) which is mounted on top of the chassis, thebottom of which is shown. Insulated leads 5B and 58 carrying signalcurrents have frequently led to costly difficulties in equipmentmanufacture. Frequently it is necessary to shield even short lengths oflead or to bend them in unpredicatable arrays to reduce interaction fromstage to stage. Using the present shielding cage the shielding of shortleads such as 55 and 58 becomes very simple. The grounding strips [2'which together comprise a cage are in this form curved convexly inwardso that when any given strip I2 is bent so as to lie parallel to thechassis it will constitute a grounding shield for a short lead, coacting(to complete 3 the shield) with the grounded chassis itself. Theremainder of the numerous strips [2 being erect will nonethelessconstitute an effective cage for the enclosed socket terminals, and forthe components associated with that socket and arranged Within the cage.In both illustrated forms of the invention the length of the strips isapproximately equal to the socket diameter, in contrast to shortgrounding lugs forming part of known sockets, which lugs have noappreciable shielding effect.

The shielding cage is primarily useful in connection with radio tubesockets. Circuit appli cations other than that illustrated, andapplications of the shielding cage to components other than radio tubesockets, will occur to those skilled in the art. The fact that thestrips are not connected to each other at their extremities makes itpossible for them to be bent away from the socket terminals for easycircuit-assembly, and also avoids troublesome coupling due to commongrounding paths and ground loops. Further features of the invention, itsapplications, and modifications of the illustrative embodiments willocour to those skilled in the art.

What I claim is:

1. .The combination of a generally circular socket having multipleterminals with a grounding and shielding cage surrounding said socketand having approximately as many strips as the socket has terminals,said strips being wide in comparison to their spacing and beingapproximately as long as the socket diameter.

2. The combination of a socket having a circular array of terminals witha grounding and shielding cage having a conductive strip extend-- ingaxially away from the socket adjacent each socket terminal for a minimumdistance equal to the diameter of the terminal array.

3. The combination of a socket having an array of terminals extendingfrom one face, and a combined grounding and shielding cage about saidsocket comprising a large number of conductive strips spaced close toeach other in relation to their width and extending substantiallyperpendicularly away from said face.

4. The combination with a socket for a radio tube or like device havingmultiple terminals on one side thereof for connection in a circuit, of agrounding ring surrounding said socket and having concave conductivestrips adapted to be bent to partially encase a circuit lead to one ofsaid terminals.

5. The combination according to claim 4 Wherein a plurality ofrelatively long and closely spaced concave strips extend away from saidside and encircle the socket.

6. A combined grounding and shielding cage comprising a generallycircular series of parallel conductive strips connected to each otheronly at one end and extending from their connection for a minimum lengthapproximately equal to the cage diameter.

7. A combined grounding and shielding cage according to claim 6 whereinsaid strips are outwardly concave.

8. A shielding structure comprising a grounding ring and at least oneshielding strip extending axially away from said ring and being concaveoutward, adapted when appropriately bent to partially encase a circuitlead.

WALTER R. JONES.

REFERENCES CITED The following references are of record in the file thispatent:

UNITED STATES PATENTS Number Name Date 2,062,256 Del Camp Nov. 24, 19362,092,930 Paradise Sept. 14, 1937

